The purpose of this study is to test the immunogenicity, safety, and tolerability of a new recombinant vaccine (PreS2+S) for hepatitis B virus. The unique aspect of this project is that in vitro T-cell responses of lymphocytes will be measured to determine whether defects in T-cell responses of lymphocytes will be measured to determine whether defects in T-cell function underlie inadequate antibody production in vaccinated subjects.